Convergence unit for color television picture tube

ABSTRACT

The illustrated convergence unit comprises three generally triangular cores adapted to be mounted around the neck of a color television picture tube at equal angular intervals. Each core comprises two legs directed inwardly toward the central axis of the tube, and crossbar means extending between the outer end portions of the legs. As to each core, the legs and the crossbar means form a triangular shape. The legs are positioned substantially along radii which extend outwardly from the central axis. Horizontal and vertical convergence coils are mounted on the legs. The triangular shape of the cores increases the efficiency of the coils. Moreover, the legs are brought into closer proximity to the three electron beams of the picture tube.

United States Patent [72} Inventor Albert M. Anthony Conneaut, Ohio [21] Appl. No. 46,311 [22] Filed June 15, 1970 [45] Patented Oct. 19, 1971 [73] Assignee Tracor, Inc. Austin, Tex.

[54] CONVERGENCE UNIT FOR COLOR TELEVISION PICTURE TUBE 7 Claims, 1 Drawing Fig.

[52] US. Cl 335/210, 313/77, 335/212 [51] Int. Cl 1101f 7/00 [50] Field of Search... 335/210, 212, 213, 298; 313/75, 76, 77

[5 6] References Cited UNITED STATES PATENTS 2,897,390 7/1959 Jensen 313/77 3,348,177 10/1967 Wood ABSTRACT: The illustrated convergence unit comprises three generally triangular cores adapted to be mounted around the neck of a color television picture tube at equal angular intervals. Each core comprises two legs directed inwardly toward the central axis of the tube, and crossbar means extending between the outer end portions of the legs. As to each core, the legs and the crossbar means form a triangular shape. The legs are positioned substantially along radii which extend outwardly from the central axis. Horizontal and vertical convergence coils are mounted on the legs. The triangular shape of the cores increases the efficiency of the coils. Moreover, the legs are brought into closer proximity to the three electron beams of the picture tube.

CONVERGENCE UNIT FOR COLOR TELEVISION PICTURE TUBE This invention relates to convergence units adapted to be mounted around the neck of a color television cathode-ray picture tube. Such a picture tube has three electron guns in spaced relation to the axis of the tube. The beam of each gun is directed to illuminate phosphor dots of a certain color on the screen of the tube. The phosphor dots are usually arranged in arrays for each color. The electron beam from each gun passes through an aperture screen or shadow mask which has a single set of holes in the same geometric configuration as each array of dots. When the electron beam travels its intended course, it illuminates only those dots which produce the intended color. The electron beams from all three guns are aimed to converge upon the holes in the mask, and thereafter the beams diverge as they pass through the holes and arrive at the screen as three individual beams.

By means of static convergence adjustments, the beams may be aimed to converge at the center of the mask, but problems arise when the beams are swept from side to side and up and down. The convergent point of the beams sweeps in an arc which moves it away from the mask at points other than the center of the mask.

Convergence coil assemblies or units have been devised and are used to meet this problem. The beams must converge on the mask so that all three beams pass through the same hole in the mask at correct angles to strike the corresponding phosphor dots on the screen. These'assemblies are known as dynamic convergence units because they correct any variations in the length from the deflection point to the apertured mask, as the beams are deflected from the center to the edges of the mask.

Prior convergence units have generally utilized a plurality of U-shaped cores having legs with horizontal and vertical convergence coils mounted thereon. The coils are energized with horizontal and vertical convergence signals developed by special circuits in the television set. These signals are effective to maintain the convergence of the three beams as they are deflected both horizontally and vertically from the center of the mask. One type of convergence unit utilizes three cores and three sets of coils thereon, spaced at equal angular intervals around the axis of the tube so as to be opposite the three electron beams.

One object of the present invention is to provide a new and improved convergence unit in which the legs of the cores are brought into closer proximity to the electron beams of the picture tube, and in which the convergence coils are enabled to operate with improved efficiency.

A further object is to provide a convergence unit which is especially well adapted for use with a picture tube having a neck of small diameter.

A further object is to provide a new and improved convergence unit which is especially well adapted for use with a picture tube in which the electron beams are deflected over an exceptionally wide angle.

Briefly, the present invention comprises a convergence unit having a plurality of cores made of a ferrite or other suitable magnetically permeable material, the cores being spaced at angular intervals around the central axis of the picture tube. Horizontal and vertical convergence coils are mounted on the cores. Each core comprises two legs with inner ends directed toward the central axis. The coils are mounted on the legs of the cores. Each core has crossbar means extending between the outer end portions of the legs. The two legs and the crossbar means of each core form a triangular shape. The legs extend generally along radii emanating from the central axis. By virtue of this construction, the legs are brought into closer proximity to the electron beams. Moreover, the coils are enabled to operate with improved efficiency.

Further objects, advantages and features of the present invention will appear from the following description, taken with the accompanying drawing, in which the single FIGURE is an elevational view, partly in section, of a convergence unit to be described as an illustrative embodiment of the present invention.

As just indicated, the drawing illustrates a convergence unit 10 adapted to be mounted around the neck of a color television picture tube 12. As in the case of most such picture tubes, the illustrated tube comprises three electron guns or the like for producing three electron beams, designated B, R and G in the drawing, for the three primary colors, blue, red and green.

In this case, the convergence unit 10 comprises three cores or core units 14, one for each of the electron beams. The cores 14 are opposite the corresponding electron beams and thus are spaced at equal angular intervals around the central axis of the picture tube 12. It will be seen that the cores 14 are mounted on frames or brackets 16, adapted to be secured to the picture tube 12 by suitable means, such as the illustrated clamp 18.

In accordance with the present invention, each core 14 is generally triangular in shape. Thus, each core 14 comprises a pair of legs 20 having their inner ends directed toward the central axis of the tube 12. Each core 14 comprises crossbar means 22 extending between the outer ends of the legs 20.

The cores 14 are made of ferrite, or some other suitable material having a high magnetic permeability, and a low-loss factor. Pole shoes 24 are preferably mounted against the ends of the legs 20 so as to spread the magnetic flux over wider areas. The pole shoes 24 are also made of ferrite or some other suitable material.

Horizontal and vertical convergence coils 26 and 28 are mounted on the cores 14. In this case, one horizontal coil 26 and one vertical coil 28 are mounted on each leg 20 of each core 14. However, the number of coils can be varied. The coils 26 and 28 are wound on bobbins 30 and 32. In the illustrated construction, the bobbins 30 for horizontal coils 26 are mounted in hollow spaces 34, formed in the bobbins 32 for the vertical coils 28. In this way, it is possible to locate both the horizontal and vertical coils 26 and 28 close to the ends of the legs 20.

It is preferred to split the crossbar means 22 so as to provide a narrow gap 36 therein. Tape or other nonmagnetic material may be mounted in the gap 36. As illustrated, an adjustable permanent magnet 38 is positioned against each crossbar means 22 so as to bridge the gap 36. By adjusting the position of each permanent magnet 38, the initial magnetic flux in the corresponding core 14 can be changed. The permanent magnets 38 are preferably disc shaped and are rotatably mounted on the frames 16 for ease of adjustment.

Because of the gap 36, each core 14 is preferably formed in two pieces 40, each of which comprises one of the legs 20 and one-half of the crossbar means 22. The pieces 40 may be moulded or otherwise formed of ferrite material. The formation of each core 14 in two pieces makes it easy to assemble the cores 14 and the coils 26 and 28.

It will be seen that the legs 20 extend inwardly from the crossbar means 22, generally along radii emanating from the central axis of the picture tube 12. Due to the triangular shape of the core 14, there is an acute angle between such radii for each pair of legs 20. Moreover, acute angles are formed between the crossbar means 22 and the corresponding legs 20.

The triangular shape of the cores 14 makes it possible to bring the inner ends of the legs 20 close together so that such ends are in close proximity to the corresponding electron beams. In this way, the efficiency of the convergence coils 26 and 28 is greatly improved. Accordingly, the convergence unit of the present invention is especially well adapted for use with a television picture tube having an exceptionally wide deflection angle. The triangular construction of the cores 14 also makes it possible to mount the convergence unit around a picture tube having an exceptionally small neck. With the triangular core construction, it is possible to use convergence coils of adequate size, while complying with very severe space limitations. The convergence unit of the present invention is exceptionally compact yet highly efficient in operation.

Various other modifications, alternative constructions and equivalents may be employed, as will be understood by those skilled in the art.

lclaim:

l. A convergence unit for a color television picture tube,

comprising a plurality of core units made of magnetically permeable material and spaced at angular intervals around a central axis,

means for mounting said core units around the neck of a picture tube,

and a plurality of convergence coils mounted on said core units,

each core unit comprising two legs with inner ends directed toward said central axis,

said coils being mounted on said legs,

each core unit comprising crossbar means extending between the outer end portions of said legs,

said legs and said crossbar means being generally in the form of a triangle.

2. A unit according to claim 1,

in which said legs extend substantially along radii emanating from said central axis.

3. A convergence unit according to claim 1,

in which there is an acute angle between the longitudinal axes of said legs of each core unit.

4. A convergence unit according to claim 1,

in which an acute angle is formed between each leg and the corresponding crossbar means.

5. A convergence unit according to claim 1,

in which corresponding acute angles are formed between said crossbar means and both legs of each core unit.

6. A convergence unit according to claim 1,

in which said coils comprise at least one horizontal convergence coil and at least one vertical convergence coil on each core unit,

7. A convergence unit according to claim 1,

in which each crossbar means is split to form a gap therein,

an adjustable permanent magnet being mounted across said 

1. A convergence unit for a color television picture tube, comprising a plurality of core units made of magnetically permeable material and spaced at angular intervals around a central axis, means for mounting said core units around the neck of a picture tube, and a plurality of convergence coils mounted on said core units, each core unit comprising two legs with inner ends directed toward said central axis, said coils being mounted on said legs, each core unit comprising crossbar means extending between the outer end portions of said legs, said legs and said crossbar means being generally in the form of a triangle.
 2. A unit according to claim 1, in which said legs extend substantially along radii emanating from said central axis.
 3. A convergence unit according to claim 1, in which there is an acute angle between the longitudinal axes of said legs of each core unit.
 4. A convergence unit according to claim 1, in which an acute angle is formed between each leg and the corresponding crossbar means.
 5. A convergence unit according to claim 1, in which corresponding acute angles are formed between said crossbar means and both legs of each core unit.
 6. A convergence unit according to claim 1, in which said coils comprise at least one horizontal convergence coil and at least one vertical convergence coil on each core unit.
 7. A convergence unit according to claim 1, in which each crossbar means is split to form a gap therein, an adjustable permanent magnet being mounted across said gap. 